It was the first major demonstration in support of gun control since the mass shooting at Sandy Hook Elementary School in Newtown, Conn. Many marchers carried signs with the names of people killed by guns, including the children and staff members gunned down at the school.
A group at the head of the march carried a large banner: "March on Washington for Gun Control: When we stand together, we stand a chance."
Norton suggested gun-control advocates can defeat the National Rifle Association, although she did not mention the group by name.
"It comes down to us because we are immune to their lobbying," she said.
Gun rights advocates held a small counter-demonstration. One man, Dick Heller, told CNN he wants armed guards in schools.
"I could not figure out why government employees have armed guards, banks have armed guards to protect the money, but the government, for some reason, thought we don't need armed guards to protect our children," he said.
The Obama administration supports a bill sponsored by U.S. Sen. Diane Feinstein, D-Calif., to restore the assault weapons ban. Duncan told the rally that while he was head of the Chicago public school system, a student died of gun violence every two weeks.
"This is about gun responsibility; this is about gun safety; this is about fewer dead Americans, fewer dead children," Duncan said.